IDFG information on Big Game Winter Feeding http://fishandgame.idaho.gov/public/wildlife/?getPage=57
The only legal restriction on feeding Big Game is in eastern Idaho. The Idaho State Department of Agriculture has rules which prohibit the feeding of Big Game in certain counties in Eastern Idaho to prevent the spread of Brucellosis http://adminrules.idaho.gov/rules/current/02/0425.pdf
I am not aware of any legal restrictions on feeding turkeys. However, feeding turkeys can result in nuisance problems.